Strobed light sources or “flashes” provide supplemental light for photographic subjects while images of the subjects are acquired by a camera or other imaging system. One common type of flash includes a xenon bulb that emits light based on the discharge of xenon gas. The spectral content of this light is fixed by the characteristics of the gas discharge, which in turn fixes the color temperature of the supplemental lighting for the photographic subject. Another type of flash, included with the cameras integrated into mobile phones, comprises one or more “white” LEDs. The “white” LEDs are typically formed using one or more blue LEDs (primary emitters) with phosphors (secondary emitters) deposited on the blue LEDs. The spectral content of the light emitted by the “white” LEDs is also fixed, depending on the spectral characteristics of the primary emitters and the emission characteristics of the deposited secondary emitters, which fixes the color temperature of the “white” LEDs typically in the range of 5500-8500 degrees Kelvin.
The characteristics of images acquired by an imaging system depend on the spectral content or the color temperature of the light. When the spectral content of the flash is fixed, desired image characteristics can be achieved by mounting color filters on the lens of the camera. However, this provides only limited control of image characteristics because the filters do not provide continuous control of the spectral content of the light received by the camera. In addition, the filters are inconvenient to use because to achieve different spectral filtering, the filters must be physically interchanged.
Based on the fixed spectra of presently available flashes and the limitations of filters used to modify spectral content of available light, there is a need for a flash that provides light with a spectral content that can be adjusted.